Adjustable length golf club

ABSTRACT

A length adjustment mechanism useful on sports and other working implements allows the length of an implement to be easily adjusted. In the case of golf clubs, the length adjustment mechanism includes a handle with a set of interior threads that engage a set of exterior threads formed on an upper end of the golf club shaft. The handle can be screwed down over the threads on the upper end of the shaft to adjust the length of the club. The handle is then fixed with respect to the shaft, and a grip is formed over the handle. The handle can be selectively repositioned along the shaft to alter the length of the club by freeing the handle, screwing it to a new position, and re-fixing the handle in the new position.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to devices for providing a golf club or other implement with length adjustability.

[0003] 2. Background of the Related Art

[0004] When a child first begins to play golf, the length of the child's golf clubs must be much shorter than clubs used by an adult. As the child grows, the ideal length of the child's golf clubs necessarily increases. To address this problem, most manufacturers create children's golf clubs in about four different lengths. The four different lengths are intended to provide the child with a club that is close to the ideal length as the child matures toward his adult height.

[0005] Unfortunately, when a child first begins to play golf, the first set of clubs is usually too long. As the child grows in height, the first set of clubs eventually become the ideal length. Then, as the child continues to grow, the clubs become too short. At some point, when the first set of clubs have become noticeably too short, the child can switch to a new set of clubs having the second length. At this point in time, the second set of clubs are too long. This process is repeated four times as the child matures toward adulthood. With each new set of clubs, the clubs are initially too long, then just right, then too short again.

SUMMARY OF THE INVENTION

[0006] The invention is a mechanism for adjusting the length of a golf club or other implement. When applied to golf clubs, such adjustable length golf clubs can be used in place of the four different length children's clubs. A golf club embodying the invention can be adjusted to any of a nearly infinite number of different lengths between its minimum length and maximum length. Thus, a set of golf clubs embodying the invention can always be set to the ideal length for a child, based on his then present height. This is in stark contrast to the prior art fixed length children's clubs, which are at a non-ideal length for most of the time, and which are only at an ideal length for four relatively short periods of time.

[0007] Because the length can be adjusted, one or two sets of adjustable length golf clubs embodying the invention can replace the four different fixed length sets usually used for children as they grow. This greatly reduces the cost of providing a child with clubs as he grows to adulthood.

[0008] In an adjustable length golf club embodying the invention, the top end of the shaft has exterior threads, or an insert with exterior threads is glued or affixed to the top of the shaft. A handle, having interior threads that cooperate with the exterior threads on the top of the shaft, is screwed down over the upper end of the shaft. A mechanism is then used to fix the handle with respect to the shaft. A traditional grip can then be mounted over the handle.

[0009] When the club is first delivered to a customer, the handle will be fully screwed down over the upper end of the shaft so that the club has its minimum length. Over time, the handle can be repositioned by unscrewing it from the top of the shaft to increase the length of the club. The handle would then be fixed in its new position.

[0010] In some embodiments of the invention, a series of length indicating marks can be formed on the upper end of the shaft. When the handle is fully screwed down over the upper end of the shaft, the handle will cover substantially all of the length indicating marks of the shaft. As the handle is un-screwed from the upper end of the shaft to increase the length of the club, the handle will gradually uncover more and more of the length indicating marks.

[0011] The invention is not limited to use on children's clubs. An adjustment mechanism embodying the invention could be used on any type of golf club that will benefit from length adjustability. For instance, a length adjustment mechanism could be used on putters so that an adult golfer could experiment with different putter lengths to determine an optimum length. In fact, the adjustment mechanism could be used for all the clubs used by an adult golfer to allow the golfer to custom tailor the length of each of his clubs to optimize his golf game.

[0012] Although the foregoing summary of the invention focuses on the advantages of the invention as used on golf clubs, the invention is not limited to golf clubs. A length adjustment mechanism embodying the invention could also be used on other types clubs and implements to provide length adjustability. For instance, an adjustment mechanism embodying invention could be used on baseball and softball bats, tennis, racquetball or badminton rackets, lacrosse or hockey sticks, kayak or canoe paddles, or any other type of implement where length adjustability would be advantageous.

[0013] Additional advantages, objects, and features of the invention will be set forth in part in the description which follows, and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention will be described in detail with reference to the following drawings, in which like reference numerals refer to like elements, and wherein:

[0015]FIG. 1 shows an adjustable length golf club embodying the invention;

[0016]FIG. 2 is a cross-sectional view showing a disassembled golf club length adjustment mechanism embodying the invention;

[0017]FIG. 3A is a cross-sectional view showing a golf club length adjustment mechanism embodying the invention in its minimum length position;

[0018]FIG. 3B is a cross-sectional view showing a golf club length adjustment mechanism embodying the invention in its maximum length position;

[0019]FIG. 4A is a cross-sectional view showing a second golf club length adjustment mechanism embodying the invention in its minimum length position;

[0020]FIG. 4B is a cross-sectional view showing the second golf club length adjustment mechanism embodying the invention in its maximum length position;

[0021]FIG. 5A is a front view of a portion of a third golf club length adjustment mechanism embodying the invention;

[0022]FIG. 5B is a right side view of the third golf club length adjustment mechanism shown in FIG. 5A;

[0023]FIG. 6 is a front view of the third golf club length adjustment mechanism in an assembled condition;

[0024]FIG. 7 is a cross-sectional view of the golf club length adjustment mechanism shown in FIG. 6, as taken along section line 7-7; and

[0025]FIGS. 8A, 8B and 8C show an adjustable length golf club embodying the invention adjusted to three varying lengths.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0026] The following specification describes an adjustment mechanism for varying the length of a golf club. Although the description is specific to a golf club, it should be understood that the invention is equally applicable to other implements where length adjustability would be desirable. For instance, a length adjustment mechanism embodying the invention could also be used on other sports devices such as baseball and softball bats, tennis, racquetball or badminton rackets, lacrosse or hockey sticks, and kayak or canoe paddles. In addition, a length adjustment mechanism embodying the invention could be used on tools and implements such as rakes, shovels, axes, hammers and other working implements.

[0027] An adjustable length golf club 20 embodying the invention is shown in FIG. 1. As shown therein, the club 20 includes a shaft 22 attached to a club head 24 and a grip or handle 26. The club is adjustable between a first length L₁ and a second length L₂. The length adjustment is accomplished by varying the position of the grip or handle 26 on the shaft 22.

[0028] A first length adjustment mechanism embodying the invention which could be used on a golf club is shown in FIG. 2. FIG. 2 shows a longitudinal cross section of the upper end of a golf club, which shows the mechanism in a disassembled state.

[0029] In this mechanism, an insert 30 is attached to an upper end of a golf club shaft 22. A receptacle 28 in the upper end of the shaft 22 receives a lower portion 32 of the insert 30. A protruding portion of the insert 30, which protrudes above the shaft 22, is cylindrical in cross section, and includes exterior threads 34. The shaft 22 and the lower portion 32 of the insert 30 can have cylindrical or other cross sectional shapes.

[0030] Several of the embodiments of the invention described in the specification include an insert mounted on an upper end of a golf club shaft. However, in other embodiments of the invention, an upper end of the shaft itself could have a cylindrical cross section, and the upper end of the shaft could include the external threads.

[0031] A hollow handle 40 includes an aperture configured to receive the protruding portion of the insert 30, and the upper end of the shaft 22. The aperture of the handle 40 includes a smooth walled portion 46 and a threaded portion 44. The internal threads 44 of the handle are shaped to cooperate with the external threads 34 on the insert.

[0032] A locking plug 50 is also provided inside the hollow handle 40. The locking plug has a cylindrical cross section with exterior threads on an outer surface thereof. The external threads of the locking plug 50 are configured to cooperate with the internal threads 44 of the handle 40.

[0033] An upper face of the locking plug 50 includes a shaped socket 52 which can be used to reposition the locking plug 50 within the aperture of the handle 40. For instance, the shaped socket may be a hex head socket which is shaped to confirm to a hex head wrench.

[0034] Alternatively, the shaped socket 52 could be shaped to cooperate with a slotted or phillips screwdriver, or some other type of driving device. The shaped socket 52 would be engaged by an appropriate driver to screw the locking plug along the threads 44 in the handle 40.

[0035]FIGS. 3A and 3B show the length adjusting assembly of FIG. 2 in two different assembled conditions. In both FIGS. 3A and 3B, the insert is affixed inside the aperture at the upper end of the shaft 22. In preferred embodiments of the invention, the lower portion 32 of the insert 30 is glued into the aperture 28 of the shaft 22. In other embodiments of the invention, the insert 30 could be affixed to the shaft using fasteners such as nails, screws or staples. In yet other embodiments of the invention, where both the insert 30 and the shaft 22 are metallic, the insert 30 could be welded to the shaft. In still other alternative embodiments of the invention, external screw threads on the lower portion 32 of the insert 30 could cooperate with internal threads in the aperture 28 of the shaft 22 so that the insert can be screwed into the aperture.

[0036] After the insert 30 is attached to the shaft 22, the locking plug 50 is screwed down the internal threads 44 of the handle 40. Initially, the locking plug 50 would be screwed substantially all the way into the handle 40, as shown in FIG. 3A.

[0037] The handle 40, with the associated locking plug 50 would then be screwed down onto the insert 30 and the upper end of the shaft 22. Once the handle has been screwed down onto the top of the shaft so that the combined length of the handle and shaft is at a desired length, the locking plug 50 would be screwed into contact with the top surface 33 of the insert 30. An appropriate driver tool can be inserted through an access hole 48 in the handle 40 to access the shaped socket 52 of the locking plug. For instance, if the shaped socket 52 is a hex socket, a hex wrench could be inserted through the access hole 48 in the handle 40 and into the shaped socket 52 of the locking plug 50. The hex wrench could then be used to drive the locking plug 50 along the internal threads 44 of the handle 40 so that the lower face of the locking plug is firmly in contact with the upper face 33 of the insert 30. This will fix the handle 40 with respect to the insert 30 and the shaft 22.

[0038] In the embodiment shown in FIG. 3A, the handle 40 has been screwed almost all the way down onto the shaft to provided the minimum combined length of the handle and the shaft.

[0039] When it is desirable to increase the combined length of the handle and the shaft, the hex wrench could again be inserted through the access hole 48 of the handle 40 and into the shaped socket 52 of the locking plug. The hex wrench could then be used to unscrew the locking plug away from the top surface 33 of insert 30. This will free the handle with respect to the shaft. The handle could then be unscrewed relative to the shaft to increase the combined length of the handle and the shaft. When the desired combined length is obtained, the hex wrench could then be used to screw the locking plug back into contact with the top surface 33 of the insert 30 to again fix the handle with respect to the shaft.

[0040] The lower portion of the handle will preferably always extend down over the working portions of the length adjusting mechanism and surround the upper end of the shaft 22. The smooth inner walls 46 of the handle 40 are configured to abut the upper end of the shaft 22 to provide a smooth outward appearance. Because the working portions of the length adjustment mechanism will be completely contained within the handle, the golf club would be indistinguishable from other ordinary clubs.

[0041] Because the handle 40 is rotated along threads on the insert 30, the golf club is adjustable to an almost infinite number of different lengths between the minimum and maximum limits. The pitch of the treads can be varied between a very fine pitch and a very coarse pitch to control the amount that the length of the club changes for each rotation of the handle with respect to the shaft. In presently preferred embodiments, the thread pitch is relatively fine so that the locking plug is as effective as possible in fixing the handle with respect to the shaft.

[0042] A second embodiment of the length adjusting mechanism is shown in FIGS. 4A and 4B. In this mechanism, the shaft 22, the insert 30, and the handle 40 are very similar to the embodiment shown in FIGS. 2, 3A and 3B. In this embodiment, however, external threads 45 are also formed on the lower outer surface of the handle 40.

[0043] In addition, in this embodiment, a collar 70 is provided to fix the handle 40 with respect to the shaft 22. The collar 70 has interior threads 72 that are configured to cooperate with the external threads 45 on the handle 40. Once the handle 40 has been screwed onto the insert 30 and the shaft 22, to provide the club with the desired overall length, the collar 70 is screwed onto the threads 45 on the lower end of the handle 40. Screwing the collar 70 onto the lower portion of the handle 40 will compress the smooth inner surface 46 of the collar against the upper end of the shaft 22 to fix the handle 40 with respect to the shaft 22.

[0044] In some embodiments of the invention, the inner surface 46 of the handle and the mating surface on the upper portion of the shaft 22 can be custom tailored to help fix the handle 40 relative to the shaft 22. For instance, the surfaces might be roughened so that the compression provided by screwing the collar 70 onto the handle 40 provides a great deal of friction between the handle 40 and the shaft 22. In other embodiments, one or both of the mating surfaces may be formed of or covered with a material having a high coefficient of friction.

[0045] In some embodiments of the invention, the lower portions of the handle 40, which have the exterior threads 45, may be tapered such that the exterior diameter of the handle increases from the lower edge of the handle up to the top of the threaded section 45. In this instance, as the collar 70 is screwed up the threaded portion 45 of the handle, the lower portion of the handle 40 will be forced against the shaft 22.

[0046] In other embodiments of the invention, the collar 70 may have an internal threaded surface 72 which increases in diameter from the lower side of the collar to the upper side. In this instance, as the collar 70 is threaded onto the handle, the handle will be forced farther and farther inward toward the shaft 22 the higher the collar 70 is threaded up the handle 40.

[0047]FIGS. 5A, 5B, 6 and 7 show a third embodiment of the invention. In this embodiment, the mechanism used to fix the handle 40 relative to the shaft 22 is a set screw.

[0048]FIG. 5A shows a side view of a shaft 22 and insert 30. Note, this view is not presented in cross-section. A groove or keyway 36 is formed on the insert 30. The groove extends in the longitudinal axial direction. FIG. 5B shows, which is a side view of the insert 30 shown in FIG. 5A, shows that the groove or keyway 36 extends inward into the insert 30 in the radial direction. In other embodiments of the invention which do not include an insert 30, and which have the exterior threads formed directly on the upper end of the shaft 22, the groove or keyway 36 would also be formed on the upper end of the shaft 22.

[0049] In this embodiment, a handle substantially as shown in the embodiment of FIGS. 2, 3A and 3B would be threaded down onto the insert 30 and shaft 22 as shown in FIG. 6. In this embodiment, however, a threaded fixation aperture passes through a sidewall of the handle. A fastener, such as a set screw 47, would be screwed into the fixation aperture, and then down into the groove or keyway 36 of the insert 30. FIG. 6 is a side view of the mechanism, with the set screw 47 partially screwed into the fixation aperture. FIG. 7 is a cross-sectional view of the mechanism taken along section line 7-7 of FIG. 6. In FIG. 7, the set screw 47 has been fully screwed down into the fixation aperture, and into the groove 36 of the insert 30.

[0050] In preferred embodiments of this form of the mechanism, a recess 49 would be formed on the outer surface of the handle 40 where the fixation aperture is formed. The head of the set screw 47 would then sit in the recess 49 so that the set screw 47 does not protrude above the outer surface of the handle.

[0051] When the user wants to adjust the length of a club having the mechanism shown in FIGS. 5A, 5B, 6 and 7, the user would first partially unscrew the set screw 47 from the handle 40 so that the end of the set screw 47 rises above the level of the insert 30. The handle 40 can then be rotated with respect to the shaft 22 to alter the combined length of the shaft 22 and the handle 40. Then set screw would then be tightened back into the handle so that the end of the set screw 47 extends into the groove 36 of the insert to fix the handle 40 with respect to the shaft 22.

[0052] In each of the embodiments described above, the exterior surface of the handle may be configured as the grip of the golf club. In other embodiments of the invention, a gripping material could be applied to the exterior surface of the handle 40 to provide a grip.

[0053] Also, in each of the embodiments of the invention, length indicating marks 60 could be applied to the shaft 22 of a golf club embodying the invention, as shown in FIGS. 8A-8C. As the handle is screwed down over the upper end of the shaft 22, the handle 40 would cover some or all of the marks. For instance, when the handle is positioned as shown in FIG. 8C, only the first three length indication marks would be showing. When the handle is repositioned to the location shown in FIG. 8B, the first six length indication marks would be shown. When the handle is again repositioned to the location shown in FIG. 8A, more of the length indication marks would be showing.

[0054] In a typical set of golf clubs, the clubs are not all the same length. The driver typically has the greatest length. The woods then get smaller in length as the degree of loft, or club face inclination increases. The irons are generally shorter than all of the woods. The length of the irons also gets smaller as the degree of loft, or club face inclination increases. For these reasons, when a golfer purchases a set of adjustable length clubs, the clubs should not all be adjusted to the same length.

[0055] By providing the clubs with length indication marks, all of the clubs can be adjusted at the same time to the appropriate length. A chart can be prepared and provided with the clubs to indicate what length the clubs should have for a given golfer height. When a child golfer has grown, and it becomes necessary to adjust the length of his clubs, all the clubs could be adjusted to have the same number of length indication marks showing. This will ensure that all the clubs in the set can be easily adjusted to an optimum length, even though no two clubs in the set will have the same length.

[0056] When adjustable length clubs embodying the invention are used for a child golfer, it is possible for the child to one, or at most two sets of clubs from childhood to adulthood. Since it is usually necessary for a child to use four or more sets of fixed length clubs to cover the same period of time, this greatly reduces the total cost of purchasing clubs over the period from childhood to adulthood. Also, since only one or two sets must be purchased, a consumer may be willing to spend more money on each set of adjustable length clubs, which would allow the clubs to be made of higher quality, more expensive materials. Further, because the adjustable length clubs embodying the invention can be adjusted at will to an almost infinite variety of different lengths, the child can always be golfing with an optimum sized set of clubs.

[0057] The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to devices and implements other than golf clubs. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. For example, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. 

What is claimed is:
 1. An adjustable length golf club, comprising: a shaft having exterior threads formed at an upper end of the shaft; a handle having an aperture configured to receive the upper end of the shaft, wherein interior threads that are configured to cooperate with the exterior threads on the shaft are formed on an inner surface of the aperture, and wherein the handle can be screwed down over the upper end of the shaft to adjust a combined length of the handle and shaft; and a releasable fixation mechanism that releasably fixes the handle with respect to the shaft.
 2. The adjustable length golf club of claim 1, wherein the releasable fixation mechanism comprises a locking plug having exterior threads configured to cooperate with the interior threads of the handle, wherein the locking plug is screwed into the handle, wherein the locking plug can repositioned within the aperture of the handle by screwing the locking plug along the threads of the aperture, and wherein a lower face of the locking plug is configured to engage an upper end of the shaft to fix the handle with respect to the shaft.
 3. The adjustable length golf club of claim 2, wherein a shaped socket is formed in an upper face of the locking plug such that a driver with a shape corresponding to the socket can be used to reposition the locking plug.
 4. The adjustable length golf club of claim 3, wherein an access hole is formed in an upper end of the handle to allow a driver to extend through the access hole and into the shaped socket of the locking plug to engage and reposition the locking plug.
 5. The adjustable length golf club of claim 3, wherein the shaped socket in the upper face of locking plug comprises a hex socket, and further comprising an access hole formed in an upper end of the handle to allow a hex driver to extend through the access hole and into the hex socket to engage and reposition the locking plug.
 6. The adjustable length golf club of claim 1, wherein exterior threads are formed on an exterior surface of a lower end of the handle, and wherein the releasable fixation mechanism comprises a locking collar having interior threads configured to cooperate with the exterior threads on the lower end of the handle, and wherein screwing the locking collar onto the exterior threads on the lower end of the handle causes the handle to be compressed against the shaft to fix the handle with respect to the shaft.
 7. The adjustable length golf club of claim 6, wherein an exterior diameter of the handle increases from the lower end to an intermediate position, such that as the locking collar is screwed onto the exterior threads on the lower end of the handle, the handle will be compressed against the shaft to fix the handle with respect to the shaft.
 8. The adjustable length golf club of claim 6, wherein an inner diameter of the locking collar decreases from a upper end of the locking collar to a lower end of the locking collar such that as the locking collar is screwed onto the exterior threads on the lower end of the handle, the handle will be compressed against the shaft to fix the handle with respect to the shaft.
 9. The adjustable length golf club of claim 1, wherein the releasable fixation mechanism comprises: a groove formed on an outer surface of the upper end of the shaft, wherein the groove extends along a longitudinal axis of the shaft; and a fastener that passes through the handle and into the groove to fix the handle with respect to the shaft.
 10. The adjustable length golf club of claim 9, wherein the fastener comprises a threaded fastener having external threads that cooperate with internal threads on a fixation aperture that passes through the handle.
 11. The adjustable length golf club of claim 9, wherein a recess is formed in the handle, and wherein when the fastener is mounted on the golf club to fix the handle with respect to the shaft, the fastener is positioned in the recess.
 12. The adjustable length golf club of claim 1, further comprising an insert that is attached to and that forms the upper part of the shaft, wherein the exterior threads formed at an upper end of the shaft are formed on the insert.
 13. The adjustable length golf club of claim 12, wherein the shaft is formed of a synthetic or composite material, and wherein the insert is formed of a metallic material.
 14. The adjustable length golf club of claim 1, further comprising length indicating marks that are formed on the shaft.
 15. The adjustable length golf club of claim 14, wherein the handle and the shaft are configured such that when the handle is positioned to minimize the combined length of the handle and the shaft, the handle at least partially covers the length indicating marks, and wherein as the handle is re-positioned to increase the combined length of the handle and the shaft, the handle will expose more of the length indicating marks.
 16. The adjustable length golf club of claim 1, further comprising a grip that is attached to an exterior surface of the handle.
 17. An adjustable length golf club, comprising: a shaft having exterior threads formed at an upper end of the shaft; a handle having an aperture configured to receive the upper end of the shaft, wherein interior threads that are configured to cooperate with the exterior threads on the shaft are formed on an inner surface of the aperture, and wherein the handle can be screwed down over the upper end of the shaft such that rotation of the handle with respect to the shaft adjusts a combined length of the handle and shaft; and means for releasably fixing the handle with respect to the shaft.
 18. An adjustable length golf club, comprising: a shaft having upper and lower ends; a club head attached to the lower end of the shaft; an insert that is inserted into and fixed to the upper end of the shaft, wherein a portion of the insert protrudes from the upper end of the shaft, and wherein the protruding portion of the insert has external threads; a handle having an aperture configured to receive the protruding portion of the insert and the upper end of the shaft, wherein interior threads that are configured to cooperate with the exterior threads on the insert are formed on an inner surface of the aperture, and wherein the handle can be screwed down over the insert and the upper end of the shaft to adjust a combined length of the handle and shaft; and a releasable fixation mechanism that releasably fixes the handle with respect to the shaft.
 19. The adjustable length golf club of claim 18, wherein the releasable fixation mechanism comprises a locking plug located in the handle and having exterior threads configured to cooperate with the interior threads of the handle, wherein a shaped socket is formed in an upper face of the locking plug such that a driver with a shape corresponding to the socket can be used to screw the locking plug along the threads in the handle to reposition the locking plug in the handle, and wherein a lower face of the locking plug is configured to engage an upper end of the insert to fix the handle with respect to the insert and the shaft.
 20. The adjustable length golf club of claim 18, wherein exterior threads are formed on an exterior surface of a lower end of the handle, and wherein the releasable fixation mechanism comprises a locking collar having interior threads configured to cooperate with the exterior threads on the lower end of the handle, and wherein screwing the locking collar onto the exterior threads on the lower end of the handle causes the handle to be compressed against the shaft to fix the handle with respect to the shaft.
 21. The adjustable length golf club of claim 18, wherein the releasable fixation mechanism comprises: a groove formed on an outer surface of the insert, wherein the groove extends along a longitudinal axis of the insert; and a fastener that passes through the handle and into the groove to fix the handle with respect to the insert and the shaft. 